Mountain streams and lakes are important refuge habitats for native fishes and are influenced by climate change through shifting thermal and hydrological regimes. Cutthroat Trout (CT; Oncorhynchus clarkii) in the southern Rocky Mountains (SRM) inhabit small fractions of their historic ranges and current populations are found in fragments of habitat in mountain streams and lakes. Therefore, a cornerstone of CT conservation strategies involves increasing the connectivity of stream and lake habitats (via increased stream length or habitat area) to provide greater habitat heterogeneity. However, a tradeoff is that upstream invasion by non-native fishes also threaten persistence of CT, and a management strategy to prevent these invasions are movement barriers that intentionally fragment watersheds.

These multiple stressors create the need to balance competing demands for increased connectivity with intentional fragmentation. Using a summary of multiple studies I will show how SRM lakes and streams are important habitats for CT conservation, different ways these habitats are warming (e.g., SRM lakes +0.47°C•decade-1 and streams +0.17°C•decade-1), and predict persistence of two sub-species of CT using a framework that incorporates multiple stressors.

About the speaker: Dr. James Roberts is a fish biologist with the USGS who has broad research expertise and investigates the ecological consequences of environmental stressors like climate change and eutrohpication for aquatic systems and specifically fish populations. Currently, he is investigating the potential effects climate change may have on the persistence of cutthroat trout (Oncorhynchus clarkii spp.) in stream and lake habitats throughout the Southern Rocky Mountains. James' other current research activities include native fish conservation, contaminants in Upper Colorado River native fish, mountain lake limnology, and bio-monitoring of Rocky Mountain transition zone streams.